Stabilization of organic substances



PatentedAug. 14,1945

I UNITED STATES j ATENH;

v 2,382,904 I smsmzsrron or oaeamc sonsrn'noss Charles J. PedersemPennsGrove, N; J., assignor to E. I. du Pont de Nemours& Company; Wtlamington, Del., a corporation of Delaware No Drawing.

, This-invention relates to the stabilization of organic substances" andparticularly to the sta- ,bilization off such substances which aresubject 3 to deterioration caused by the action of molecular 1 oxygenand catalyzed'by metals and their com- ;pounds' a Many organic products,'suchas fats, drying oil, rubber, petroleum products, photographicdevelopers and synthetic unsaturated com-" 1 pounds, are'readily'attacked by oxygenand the'lo resulting; deterioration impartsundesirable qualities to thein'and eventually destroys their iusefulness.

Signal success has been achieved in recent v oxidized inthe course oftime, as a result of autooxidation, thebeneficial eflect obtained by'their 1 useis notpermanent, and theyprotect theorganic substancesonly solongas they are. not

rendered inactive. They are, moreover, very specific in action, each;group of auto-oxidizable substances requiring a different .oxidantforthe best results. ,Vanadium, chromium,

cobalt, copperand their catalytically "active compounds accelerate therate -of oxidation of many [organic substances. For. example, it is.well lmown that copper compounds speed the forma.'-' tion of gumincracked gasoline and the aging orrubber; .thatcobaltcompounds promotethe pounds catalyze the deterioration of lubricating 1 oils. They alsoaccelerate. the oxidation of aromatic. hydroxyand' amino antioxidantsused to stabilize these oxidiz'able substances. Hence, these metalcatalysts and the antioxidants are antagonistic in action, and thenormal inhibit presence of the former.

, Metal compounds occur naturally in many organic products, but.o'iten-insuch slight traces ing eflect of the latter is greatly reducedin the as to cause very little. harm. Their concentra- ,tions', however,are frequently raised during the? course of. handling and utilizingtheproducts??- manganese,- iron,

Application October-1 0, 1942; sci-a m. 461,632

1c Claims. -(c1. zoo-v99 copper or iron are used for storage andtransportation, 'or ingredients contaminated with metal compounds mightbe added.

The harm done by these extraneous catalysts maybe prevented by at leastthree methods:

' f 1) theirremoval by purification, but often this s is practicallyimpossible ofaccomplishment and usually too costly to be economicallyfeasible, (2) the addition of a sufiicient amount of an antioxidant sothat its preservin eiifectis equal or greater than the pro-oxidantefifects of the metal catalysts present, but. the efiectiveness of theantioxidant is so greatly diminished by the metal catalysts that theadvantage gained under this circumstance is seldom worth the cost of theincreased quantity of antioxidant requiredior adequate stabilization,and (3) the suppression of the catalytic activity of the metal compoundsby chemical means without physically removing them -from the system.

It is an object of the present invention to re tard the deterioration oforganic substances caused by the action/of molecular oxygen and promotedby the presence of certain, metal catalysts and their catalyticallyactive compounds.

Another object is to render antioxidants, which are relativelyineffective in the presence of metal catalysts and their catalytically*active compounds, efiective to inhibit the oxidation of oxidizableorganic' substances even in the presence of metal catalysts and theircatalyticallyactive compounds. A further object is to provide a newclass of metal deactivators-which are efiective to render metalcatalysts inactive I I to catalyze the oxidation of oxidizableorganic joxidation of dryin oils; andthat iron "comsubstancescontaining orin'contact with such metal catalysts. A'more particular object is toinhibit the deterioration of petroleum hydrocarbans in the presence ofmetal catalysts and their 40 catalytically active compounds. Otherobjects are to provide new compositions of matter and/ to advance theart. .Still other objects will appear'hereinafter The above and otherobjects may be accom- 5 plished in accordance with my invention whichcomprises adding to organic substancea normally subjectto deteriorationcaused by the action of molecular oxygen, and; containing ,a cat alystof the'group of chromium, iron, copper and vessels and conduits made ofmetals containin their 901 normally fl v to a y e oxidation of suchorganic substances, a small proportion of an antioxidant, normallyefl'ective -to materially retard such deterioration in the absence ofsaid catalyst, but which is less efiective in the presence of saidcatalyst, and a small proportion, sufllcient to deactivate saidcatalyst, of-a metal deactivator having the formula wherein'A and B aredivalent organic radicals, aromatic in nature, in which the freevalences are on adjacent carbon atoms. I have found that such metaldeactivators are capable of effectively suppressing the catalyticactivity of chromium, iron, copper and their catalytically activecompounds and hence will render such catalysts ineffective to catalyzethe oxidation of the organic substance and the antioxidant and willrender the antioxidant eifective to retard the oxidation of the organicsubstance.

The organic substances, which may be treated in accordance with myinvention, include animal and vegetable fats and oils, edible oils,fruit and vegetable juices, textile fibres, photographic developers,antioxidants, synthetic unsaturated compounds, petroleum hydrocarbons,rubber and the like. My metal deactivators are particularly desirable inrubber and in liquid petroleum hydrocarbons and especiallyin-gum-forming hydrocarbon distillates, such as, for example, crackedgasoline. The organic substance, particularly the petroleumhydrocarbons, will also contain an antioxidant which is normallyeffective to materially retard the deterioration or oxidation of theorganic substance in the absence of the catalytically active metal, butwhich is less effective in the presence of such metals.

The metal deactivators of myinvention comprise the broad group ofcompounds represented by the formula wherein A and B are the same ordifferent div'alent organic radicals, aromatic in nature, wherein thetwo free valences are on adjacent carbon atoms. It is not necessary thatboth A and B be aromatic radicals, that is, contain benzene rings,provided they are aromatic in nature so that the hydroxyl groupsattached to the radicals are phenolic in character rather thanalcoholic. The radicals A and B may contain .nonhydrocarbon radicals,such as nitro' and sulfonic groups, but such groups are generallyundesirable since they reduce the weight effectiveness of the Icompounds and, unlike the hydrocarbon substituents; tend to decrease thesolubility of the com-,- pounds in organic subflances. Preferably, themetal deactivators are free of strongly acidic substituents. Alsopreferably, both A and B are divalent organic radicals of the benzene,naphthalene and pyrazolone series in which the free valences are onadjacent ring carbon atoms. The most effective compounds appear to bethose in which both A and B are divalent aromatic radicals, particularlyof the benzene series, in which the free valences are on adjacent ringcarbon atoms in benzene rings. I particularly prefer azcbenzene whichcontains, as the sole su-bs'tituents,

from 2 to 4 hydroxy groups, each benzene ring having a'hydroxy group inthe position ortho to the sac group.

Definite operative concentrations of the metal deactivator in theorganic substance cannot be specified for each case as the quantityrequired is dependent upon the amount of metal catalyst present in theorganic substance. The metal deactivator should be present in theproportion of approximately 5 to 10 times the amount of the metalcatalyst present, on the basis of the metallic element in order toobtain complete deactivation of the metal catalyst. Higher proportionsof metal deactivator maybe employed, particularly when a reservoir ofmetal is present in the form of metal in bulk in contact with theorganic substance. Generally, from about'il.000l% to about 0.1%, basedon the weight of the organic substance, will be suflicient for mostpurposes, particularly when the organic substance is a liquidpetroleumhydrocarbon, such as a gum-forming hydrocarbon distillate of thecharacter of cracked gasoline. -When the organic substance is rubber, itwill generally be desired to employ larger amounts of the metaldeactivators up to about 1% and preferably in the proportion oi about0.5%.

The catalytically active metal and its. compounds may be dissolved inthe organic substance or suspended therein or may be in the form of,

metal in bulk in intimate contact with the organic substance. It will beunderstood that, when I refer to an organic substance containing acatalyst, I mean to include those cases wherein the metal in bulk formis in contact with the organic substance, as well as those cases whereinthe catalytically active metal is dissolved or suspended in the organicsubstance. .1

The deactivators may be added to the oxidizable organic substances to.be protected in any form and manner. They may be in solid or liquidform, mixed with other additional agents or dissolved in a solvent. Theymay be dissolved in the organic substance or dispersed therein in anysuitable manner. They may be added to the finished organic substance orto the organic substance at any stage in its manufacture.

In order to avoid confusion arising from a superabundance of data,cracked gasoline has been selected as an example of an auto-oxidizableorganic substance for the purposes of illustration. The samples ofgasoline used in the following tests were either cracked gasolines orblends of cracked and straight-run gasolines, completely refined, butotherwise untreated with chemical agents, such as dyes, anti-knocks andantioxidants. Since gasoline is a mixture of variable composition,identical results are not obtained with different samples. The magnitudeof the effects is great enough, however, to render this differencerelatively insigniflcan p-Benzylarninophenol, abbreviated BAP, has beenchosen as a representative gasoline antioxidant. The metals, present ascatalysts, were employed as their oleates. The concentrations of theantioxidants and the metal deactivators are crease its induction periodin the absence of added metal catalysts.

The accelerated method, used for determining the induction periods givenbelow, was the one described in J. I. E. C. 25. 897 '(1933). It consistsin heating cc. of gasoline at 100 C. in

a 1 liter Pyrex flask containing pure oxygen. The internal pressure isobserved every 10 minutes by means of a manometer attached to the sys r2,882,904 3 tem. The elapsed time from the start of the test1-phenyl-3-methyl-5-pyrazolone is until the gasoline begins to absorboxygen at the CHPC=N rate of 10 cc. .per 10 minutes or higher, as shown3 2 IN c by the fall in internal pressure, is taken as the 4 5 inductionperiod. It has been found that the 5 B1 induction period, obtained bythis method. al- 0 thhugh greatly shortened, is a fairly accurate mmmeasure of the relative stability of gasoline under g fiz igig g l tfi zfi g zz tzgg i normal storage conditions.

I Table 1 J=N /a 2 [Induction period of control100 minutes] N=N--C4\ 51| [Tiliilig gasoline, conia2in%)ng 0.001% BAPband hatving an H CN\ miesi:; 2:...i..e We no can Acetoacetauilideis Induction period in minutesCHP;C cHi-c-NH C@HE Cone. Cu 00017 No deactivam g Diazotizedz-aminophenol coupled to acetoacetazobenzene anilide (No. 8 in abovetable) is 0 510 so 230 -NHC H N=N-HC 1 As cupric cleats. 25 C-CHa u Itwill be observed that, at 0.001%, 2,2'-dihy- B0 droxyazobenzenesuppresses almost completely Table IV the catalytic activity of 0.0001%soluble copper. v

T bl H No. g g f, 8: Compound Cone. Ind.per

A: r No megglll c Compound Cone. Ind. per.

It will be observed that the catalytic action of metallic copper issuppressed by the azo compound.

It is not necessary that both A and B in HOAN=N-B-OH be aromaticradicals, provided they are aromatic in nature, that is, the hydroxylgroups attached to the radicals are phenolic in property rather thanalcoholic.

The action of a number of such effective com Pounds are shown in TableIn.

Table m Compound \Diazotized 2-aminophenol coupled to acetoacetanilide.

do 2, 4, 6, 2'-tetra-hydroxyazobenzcne 0.001 260 2, 4,B-trihydroxyazobenzene 0.001 150 It will be noted that, while2,4,6,2'-tetrahydroxyazobenzene (No. 4) overcomes the catalytic effectof copper, 2,4,6-trihydroxyazobenzene (No. 5) is inert, indicating thatthe mere presence of two ortho-hydroxyl groups does not confer metaldeactivating power, but that it is necessary that at least oneortho-hydroxyl group be present on each side of the azo linkage.

There are groups, besides the hydroxyl, such as the amino and thecarboxyl, which confer metal deactivating power, but they are lesseifective. This is shown in Tables V and VI.

Table v No Com und 0 Ind BAP on p0 one. .per.

.' .o I I do 2, 4, 2-trihydroxy-\ azobeuzene 0.0011 300 5 0.001 1.0Z-hydroxy 2', 4'diaminoazobenzene... 0. 005 210 Table VI No. 83 CompoundGone. 35:

Wt. P. P. M. Wt. '7 Minutes 1 0.0 0.0 None 180 2 0.002 0.0. 370 3 0.0021.0 do 30 4 0.002 1.0 2, 4, 2'-triliydroxyazobenzene 0.002 350 -5 0.0021.0 Z-hydroxydmcthylxy-azobenzene 0.005 240 the oxidation of manyorganic products.

Copper is one of the most potent catalysts for It is the most powerfuland one of the commonest metal contaminants in gasoline. Other metals,

, however, possess diil'erent degrees of catalytic activity.

The action of certain catalysts on stabilized gasoline and the effectsof 2,2,4'-trihydroxyazobenzene on their activity are shown in Table VII.

Table VII [Induction period of control-130 minutes] [This gasoline,containing 0.002% p-(n-butyi-amino)-phenol and having an inductionperiod or 505 minutes in the absence of metal catalysts,was used for thetests, the results of which are presented below.]

Induction period in minutes No; Metal catalyst 1 Cone. 000296 2,

No deac- 4'-trihytivator droxyazobenzene P. P. M.

1'. Chromium 0. 81 475 505 2 Iron 0.87 486 505 3 Copper l. 50 525 i Themetal catalysts were added as the oleates.

It will be noted that chromium and iron, besides copper, shorten theinduction period of stabilized gasoline, and that 2,2',i'-trihydroxyazo-v benzene counteracts the action of all these metals.

The deactivators are also eflective in decreas-' ing the copper dishgum, whenused in combination with an antioxidant. 'This is shown by thedata in Tables VIII and IX.

physical test was used as a method of evaluation.

The following stock was used in the tests.

Rubber 100 Zinc oxide 100 Sulfur 3 Stearic acid 1 Lithopone 20Di-o-tolyl guanidine 0.75 Phenyl-p naphthylamine 1.0 Copper stem-at 0.05

The stock was cured for minutes at 40 pounds steam pressure. The resultsof the bomb tests are given in Table X.

Table X Days at pound added no y methylazo- No C. and benzene 300 lbsoxygen Ten- Ten- Tensile 1 e1. sile sile el.

1 Tensile strength in lbsJsq. in. 3 elon ation. v Melte oil.

It will be noted that, while the compound having an ortho-hydroxyl groupon each side of the we linkage is effective, that having anorthohydroxyl group on only one side is not. 4

It will be understood thatthe experiments and tests, hereinbeiore given,have been given for illustrative purposes only. Many variations andmodifications can be made in my invention without departing from thespirit or scope thereof.

It has long :been recognized that small traces of copper have a verypronounced catalytic effect on the oxidation of rubber. In order toovercome this difliculty, it has been necessary to establish rigorousspecifications for the copper content of compounding agents used inrubber. In many cases, particularly with dyes, the removal 0d traces ofcopper is both troublesome and ex pensive.

In general, the common antioxidants used in rubber are unable tosuppress the catalytic action of copper. The metal deactivators,however, have been found to be eiiective for this purpose.

Since the am compounds of my invention are not antioxidants, generally,they were tested in arubber stock containing 1% or phenyl-p-naph-iithylamine as an added. antioxidant. The bomb The metal deactivators ofmy invention can be.

employed in other organic substances, the metals may be present in otherforms and other compounds, within the broad scope of my invention, maybe substituted for the compounds specifically referred to hereinbefore.While I have disclosed the use of single metal deactivators, it will beapparent that mixtures of two or more metal deactivators o! my inventionmay be employed if desired.

Besides many others, the following compounds are metal deactivatorswithin the scope of my invention;

- 2,2'.,4'-trihydroxy-5- (ter.-butyl) -azobenzene2,2-dihydroxy-5,5'-dimethylazobenzene 2,2'-dihydroxy-5,5' -di-(ter.-butyl) -azobenzene 2.2'-dihydroxy-3,3',5,5'-tetramethylazobenzene2-hydroxy-5- (ter.-butyl) -phenylazo-beta naphthol2,2',4,4'-tetrahydroxyazobenzene Diazotized I Z-amino-i-(terz-butyl)-phenol coupled to 1-phenyl-3-methyls5-pyrazolone 'Diazotized2-amino-4-methylphenol' coupled to acetoacetanilide I Digitized3-amino-2-naphthol coupled to resor- It will be apparent that, by myinvention, I am able to effect the stabilization of organic substancessusceptible to the harmiul action of molecular oxygen catalyzed bychromium, iron, copper and their catalytically active compounds. Thisstabilization may be accomplished, in accordance with my invention, bythe-addition oi aseaooa metal deactivators in combination with an amountof an antioxidant, suilicient to stabilize the substance in the absenceof the metal catalyst. It is technically and economically unfeasible tocounteract the catalytic effects of such metals by means of anantioxidant alone. I believe that the metal deactivators of my inventionfunction by forming very-stable complexes with the metals,whichcomplexes are catalyticalLv inactive. It appears that the metaldeactivators of my invention, in general, are not antioxidants and forpractical purposes, they must be employed in combination withantioxidants. It will be understood that, while I have advanced a theoryas to the action of the metal deactivators,

my invention is not to be limited by any theory as to the manner inwhich the metal deactivators function to produce the results.

I claim:

1. A composition comprising an organic substance, normally subject todeterioration caused by the action of molecular oxygen, containing acatalyst of the group consisting of chromium, iron, copper and theircompounds, normally effective to catalyze oxidation of said organicsubstance, a small proportion of an antioxidant, normallyefl'ective tomaterially retard such deterioration in the absence of said catalyst butwhich is less .eflective in the presence of said catalyst, and havingincorporated therein a metal deactivator, in a small proportions'uflicient to deactivate said catalyst, having the formula stance, asmall proportion of an antioxidant,

normally effective to materially retard such deterioration in theabsence of said catalyst but which is less effective in the presence ofsaid catalyst, and having incorporated therein a metal deactivator, in asmall proportion sumcient. to deactivate said catalyst, having theformula HOA-N=NBOH wherein A and B are divalent organic radicals of thegroup consisting of the radicals of the benzene, naphthalene andpyrazolone series in which the free valences are on adjacent ring carbonatoms and which metal deactivator is free of substituents more stronglyacidic than phenolic catalyst, and having incorporated therein a metaldeactivator, in a small proportion suflicient to deactivate saidcatalyst, having the formula HO-AN= N-BOH wherein A and 2B are divalentaromatic radicals in which the free valences are on adjacent ring carbonatoms in benzene rings and which metal deactivator is free ofsubstituents more strongly acidic than phenolic hydroxy groups, theantioxidant and the metal deactivator being diil'erent chemicalcompounds.

4.- A composition comprising an organic substance, normally subject todeterioration caused by the action of molecular oxygen, containing acatalyst of the group consisting of chromium, iron, copper and theircompounds, normally effective to catalyze oxidation of said organicsubstance, a small proportion of an antioxidant, normally eilective tomaterially retard such deterioration in the absence of said catalyst butwhich is less effective in the presence of -said catalyst, and havingincorporated' therein a metal deactivator'in a small proportionsufficient to deactivate said catalyst which metal deactivator is a2,2'-clihydroxyazobenzene which is free of substituents more stronglyacidic than phenolic hydroxy groups, the'antioxidant and the metaldeactivator being different chemical compounds.

5. A composition comprising an organic substance, normally subject todeterioration caused by the action of molecular oxygen, containing a.catalyst of the group consisting of chromium, iron, copper and theircompounds, normally efiective to catalyze oxidation of said organicsubstance, a small proportion of an antioxidant, normally effectivetomaterially retard such deterioration in the absence of said catalystbut which is less eflective in the presence of said catalyst, and havingincorporated therein a metal deactivator in a small proportion sumcientto deactivate said catalyst which metal deactivator is azobenzenecontaining, as the sole substituents, from '2 to 4 hydroxy groups, eachbenzene ring having a hydroxy group in the position ortho to the azogroup, the antioxidant and the metal deactivator being diflerentchemical compounds.

6. A compositioncomprising an organic substance, normally subject todeterioration caused hydroxy groups, the antioxidant and the metal ldeactivator being different chemical compounds.

3. A composition comprising an organic substance, normally subject todeterioration caused by the action of molecular oxygen, containing a.catalyst of the group consisting of chromium, iron, copper and theircompounds, normally effective to catalyze oxidation of said organicsubstance, a small proportion of an antioxidant, normally efiective tomaterially retard such deterioration in the absence of said catalystbutwhich is less effective in the presence of said drocarbons,

by the action oi molecular oxygen,-containing a catalyst of the groupconsisting of chromium,

iron, copper and their compounds, normally effective to catalyzeoxidation of said organic substance,\a small proportion of an,antioxidant,

normally effective to materially retard suchv deterioration in theabsence of said catalyst but which is less eflective in the presence ofsaid catalyst, and having incorporated therein a metal deactivator in asmall proportion sufflcient to deactivate said catalyst which metaldeactivator is 2,4,2-trihydroxyazobenzene, the antioxidant and the metaldeactivator being diiferent chemical compounds.

7. A composition comprising petroleum hynormally subject todeterioration caused by the action of molecular oxygen, containing acatalyst of the group consisting of chromium, iron, copper and theircompounds, normally effective to catalyze oxidation of said petroleumhydrocarbons, a small proportion of an antioxidant, normally efiectiveto materially retard such deterioration in the absence of said catalystbut which is less effective in the presence of said catalyst, and havingincorporated therein a metal deactivator, in a small proportionsufllcient to deactivate said catalyst, having the formula 1' wherein Aand B are divalent aromatic radicals in which the free valences are onadjacent carbon atoms, the antioxidant and the metal deactivator beingdiiierent chemical compounds.

8. A composition comprising petroleum hydrocarbons, normally subject todeterioration caused by the action of molecular oxygen, containing acatalyst of the group consisting of chromium,

iron, copper and their compounds, normally effective to catalyzeoxidation of said petroleum hydrocarbons, a small proportion of anantioxidant, normally eflective to materially retard such deteriorationin the absence of said catalyst but which is less effective in thepresence of said catalyst, and having incorporated therein a metaldeactivator, in a small proportion sufllcient to deactivate saidcatalyst, having the formula wherein A and n are divalent organicradicals of the group consisting of the radicals oi the benzene,naphthalene and pyrazolone series in which the free valences are onadjacent ring'carbon atoms and which metal deactivator is free ofsubstituents more strongly acidic than phenolic hydroxy groups, theantioxidant and the metal deactivator being different chemicalcompounds.

wherein A and B are divalent aromatic radicals inwhich the free valencesare on adjacent carbon atoms and which metal deactivator is free ofsubstituents more strongly acidic than phenolic 'hydroxy groups, theantioxidant and the metal deactivator being different chemicalcompounds.

10; A composition comprising cracked gasoline, normally subject todeterioration caused by the action of molecular oxygen, containing acatalyst of the group consisting of chromium, iron, copper and theircompounds, normally effective to catalyze oxidation of said crackedgasoline, a small proportion of an antioxidant, normally effective'tomaterially retard such deterioration in the absence of said catalyst butwhich is less effective in the presence of said catalyst, and havingincorporated therein a metal deactivator, in a small proportionsuilicient to deactivate said catalyst, havingthe formula HOAN=NB-OHwherein A and B are divalent-organic radicals of the .group consistingof the radicals of the benzene, naphthalene and pyrazolone series inwhich the free valences are on adjacent ring carbon atoms and whichmetal deactivator is. free of substituents more strongly acidicthanphenolic hydroxy groups, the antioxidant and the metal deactivatorbeing different chemical compounds.

11. A composition comprising cracked gasoline, normally subject todeterioration caused by the action of molecular oxygen, containing acatalyst of the group consisting of chromium, iron, copper and theircompounds, normally ef-' fective to catalyze oxidation of said crackedgasoline, a small proportion of an antioxidant, normally effective tomaterially retard such deterioration in the absence of said catalystbutwhich isless eflective in the presence of said catalyst, and havingincorporated therein a metal deactivator in a small proportion sum-'cient to deactivate said catalyst which metal deactivator is azobenzenecontaining, as the sol: substituents, from 2 to 4 hydroxy groups, eachbenzene ring having a hydroxy-group in the position ortho'to the azo'group, the antioxidantand the metal deactivator being different chemicalcompounds.

12. A composition comprising cracked gasoline, normally subject todeterioration caused by the action of molecular oxygen, containing acatalyst of the group consisting of chromium, iron, copper and theircompounds, normally elective to catalyze oxidation of said crackedgasoline, a small proportion of an antioxidant, normally effective tomaterially retardsuch deterioraflm in the absence of said catalyst butwhich is less eflective in the presence of said catalyst, and havingincorporated therein. ametal deactivator in a small proportion sumcientto deactivate said catalyst which metal deactivator is2,4,2'-trihydroxyazobenzene, the antioxidant and the maal deactivatorbeing different chemical compounds.

13. A composition comprising rubber, normally subject to deteriorationcaused by the action of molecular oxygen, containing a catalyst of thegroup consisting of chromium, iron, copper and their compounds, normallyeifective to catalyze oxidation of said rubber, a small proportion of anantioxidant, normally eifective to materially retard such deteriorationin the absence of said catalyst but which is less effective in thepresence of saidcatalyst, and having incorporated therein a metaldeactivator, in a small proportion suilicient to deactivate saidcatalyst. having the formula wherein A and B are divalent aromaticradicals in which the free valences are on adjacent carbon atoms, theantioxidant and the metal deactivator beingdii'lferent chemicalcompounds. 14. A composition comprising rubber, normally subject todeterioration caused by the action 0! molecular oxygen, containing acatalyst of the group consisting of chromimn, iron, copper an theircompounds, normally effective to oxidation of said rubber, a smallproportion of Y an antioxidant, normally eflective to materially retardsuch deterioration in the absence of said catalyst but which is lesseffective in the presence.

of said catalyst, and having incorporated therein ametal deactivator, ina small proportion suflicient to deactivate said catalyst, having theformula aasaeoa which the free valences are on adjacent rin carbon atomsand which metal deactivator is free of substituent more stronglyfacidicthan phenolic hydroxy groups, the antioxidant and the metal deactivatorbeing difierent chemical compounds.

15. A composition comprising rubber, normally subject to deteriorationcaused by the action of t molecular oxygen, containing a catalyst of thegroup consisting of chromium, iron, copper and 16. The method ofinhibiting the catalytic oxidation of an organic substance caused by acatalyst of the group consisting of chromium, iron, copper and theircompounds which comprises incorporating in said oragnic substance asmall proportion of an antioxidant, normally effective to materiallyretard such deterioration in the absence of said catalyst but which isless their compounds, normally efiective to catalyze oxidation of saidrubber, a small proportion of an antioxidant, normally eii'ective tomaterially retard such deterioration in the absence of said catalyst butwhich is less effective in the presence of said catalyst, and havingincorporated therein ametal deactivator inasmall proportion suflicientto deactivate said catalyst which metal deactivator is2,4,2'-trihydroxyazobenzene, the antioxidant and the metal deactivatorbeing diflerent chemical compounds.

efiective in the presence of said catalyst, and a small proportion,suflicient to deactivate said catalyst, of a metal deactivator havingthe formula HO-A-N=N-B-OH wherein A and B are divalent organic radicalsof the group consisting of radicals of the benzene, naphthalene andpyrazolone series, in

which the free valences are on adjacent carbon atoms, the antioxidantand the metal deactivator go being different chemical compounds.

CHARLES J. PEDERSEN.

